1. Field of the Art
This invention relates to a rotating head assembly suitable for application to digital video tape recorders or the like, and more particularly to a signal transmission path arrangement on such a rotating head assembly.
2. Description of the Prior Art
Illustrated in FIGS. 2 and 3 is a conventional rotating head assembly for digital video tape recorder, wherein upper and lower stationary drums 2 and 3 which are located coaxially on the upper and lower sides of a head rotating body 1 are integrally fixed to each other at one side by means of a drum holder 4. The head rotating body 1 is constituted by a rotary flange 1a which is fixedly mounted at its center on the upper end of a vertical rotational shaft 5, and a rotatary disc 1b which is securely fixed on and along the outer periphery of the rotary flange 1a. The lower end of the rotational shaft 5 is directly coupled with the output shaft of a motor 6 which is fixedly mounted on a lower portion of the lower stationary drum 3. The rotational shaft 5 is rotatably supported through a bearing 3b in a vertical cylindrical portion 3a which is integrally formed at the center of the lower stationary drum 3.
For recording and/or reproducing video signals, paired rotating heads, namely, a pair of erasing heads 7, a pair of recording heads 8 and a pair of reproducing heads 9 are mounted on the lower side of outer peripheral portions of the rotary disc 1b on the head rotating body 1 at an angular interval of 180.degree.. These plural number of heads 7 to 9 are protruded radially outward through a gap 10 between the upper and lower stationary drums 2 and 3. For recording and/or reproducing a magnetic tape (not shown) which is transported helically along the outer peripheries of the upper and lower stationary drums 2 and 3, the plural number of heads 7 to 9 are rotationally driven from the motor 6 together with the head rotating body 1 through the rotational shaft 5.
In this conventional rotating head assembly, a cylindrical portion 1c which is integrally formed in a lower portion of the rotary flange la of the head rotating body 1 is concentrically fitted around the outer periphery of the afore-mentioned cylindrical portion 3a. Three sets of rotary transformers 11 to 13 for transmission of signals to or from the erasing heads 7, recording heads 8 and reproducing heads 9 are located between the cylindrical portions 1c and 3a in series in the axial direction (in three successive positions in the axial direction).
For instance, the signal transmission path A for the erasing head 7 is routed from a harness 14a to the stator 11a of a rotary transformer 11 in the lower position through an annular relay board 15 mounted on an inner bottom portion of the lower stationary drum 3 and a harness 16a, from the rotor 11b of the transformer to a common substrate board 19 of annular shape through a harness 20a, a common annular relay board 17, mounted on upper portions of the rotary flange 1a and rotary disc 1b of the head rotating body 1, and a contact 18a, and from the common substrate board 19 to the erasing head 7 through a harness 21a.
Further, for instance, the signal transmission path B for the reproducing head 9 is routed from a harness 14b to the stator 12a of a rotary transformer 12 in the middle position through a relay board 15 on an inner bottom portion of the lower stationary drum 3 and a harness 16b, from the rotor 12b of the transformer to the common substrate board 19 through a relay board 17 on an upper portion of the head rotating body 1 and a contact 18b, and from the common substrate board 19 to the reproducing head 9 through a harness 21b. The signal transmission path for the recording head 8 is routed in a similar manner by the use of the rotary transformer 13 in the upper position.
In this instance, a plural number of spacers 22 are interposed between the rotary transformers 11 to 13 to prevent crosstalk between signals in the respective signal paths.
However, the above-described arrangement of the conventional rotating head assembly, having the three rotary transformers 11 to 13 located in series in the axial direction and having a plural number of spacers interposed between these rotary transformers 11 to 13 for the purpose of preventing crosstalk of the respective signals, suffers from a problem that the rotating head assembly as a whole needs to have a relative large height in the axial direction.
Besides, since the signal transmission paths between the rotors 11b, 12b and 13b of the rotary transformers 11 to 13 and the respective heads 7 are all routed through the common substrate board 19 which is mounted on an upper portion of the head rotating body 1, it has been necessary to pay special attention to the circuit arrangement on the common substrate board 19 or to employ shield cases or other countermeasures to prevent the crosstalk between the signals being passed through the common substrate board 19, resulting in an increased number of component parts or an increased number of steps in the assembling process, which is reflected by a higher cost.